How to simulate FSS in CST

Hello everybody, I'm student and I am trying to simulate an EBG in CST.
Actually, I want to get the reflection phase of FSS in CST for mush-room design,
but I don't know how to set port and mode simulate for FSS.
In my design, reflection phase 0 frequency is 2.45 ( I refer it in a paper ).
Could you help me set port and show me how simulate it, I read a design of FSS
in CST help (there is just one example but they don't write out what I want, maybe
I don't understand how they get it result).

Thanks!

Can you attach the reference paper.

You can search in google engine, it's free and easy to find, here is it's name:
"Numerical Analysis of Mushroom-Like and Uniplanar EBG Structures Utilizing Spin Sprayed Ni (–Zn)–Co"
But, it's just design parameters, I want to know what does FSS mean, you can now search the key word "FSS"
in CST help, I can't do the simulation in this help.